1. Field of the Invention
The present invention relates generally to sound transducers, and more specially to an apparatus and system for altering the angular position of the transducer and processing the information obtained therefrom.
2. Description of the Prior Art
Ultrasonic detection equipment is routinely used in industry for nondestructive testing of solid materials. For example, steel pipes and plates can be checked for flaws or bad welds by applying pulses of ultrasonic energy to the metal and observing the reflected energy.
Ultrasonic inspection of steel materials is presently an inefficient and time consuming process. An ultrasonic transducer must be moved, by machine or by hand, over the entire surface of the test material being inspected. In order to more accurately determine the subsurface structure of the test material, and to better pinpoint any flaws, this scanning action is repeated with the ultrasonic energy pulses being emitted into the test material at several different angles of incidence. For example, the test material can be scanned with the incident ultrasonic energy impinging thereon at refracted angles of 0.degree., 45.degree., and 60.degree.. When three such angles are chosen, three complete scans of the test material must be made. Inasmuch as the testing procedure is identical in all three cases except for the incident angle of the ultrasonic energy, such a process is inefficient.
The prior art shows several methods of changing the incident angle of the ultrasonic energy. One method is to use several different blocks, commonly known as wedges, each of which is shaped so that the transducer transmits the ultrasonic energy at a predetermined angle with the surface of the test material. These blocks are typically made of plexiglass or other material which transmits ultrasonic energy, and are carefully machined to predetermined angles to produce refracted angles, such as the 0.degree., 45.degree., and 60.degree. mentioned above. The ultrasonic transducer is attached to this wedge, and passed over the surface of the test material. The transducer is then moved to the next wedge, and the process is repeated. Alternatively, each wedge can have its own transducer, as long as they are carefully matched.
An alternative to the use of individual fixed angle wedges is the use of a single housing which can move a single transducer to various angles. Examples of such devices are shown in U.S. Pat. No. 3,938,372 issued to Sproule, and U.S. Pat. No. 2,602,102, issued to Webb. These variable angle housings allow the use of a single transducer and a single wedge substitute. The incident angle can be set to a first desired value and the scanning process of the test material undertaken. The angle can then be changed, with the scanning process repeated. Although such variable angle housings are an improvement over multiple fixed angle wedges, they still require that the test material be scanned once for each of the preselected test angles.
Since it would be desirable that the complete test be accomplished with a single scan of the test material, it is an object of the present invention to provide an apparatus which is capable of scanning the test material at multiple preselected angles on a single pass. It is a further object of the present invention to provide a system which selects and records the ultrasonic reflection information corresponding only to the preselected angles of incidence.